Catalyst for Catalytic Cracking Fluidized Bed

ABSTRACT

The present invention relates to a catalyst for catalytic cracking fluidized-bed, and the technical problems to be primarily solved by the present invention are high reaction temperature, low cryogenic activity of catalysts and worse selectivity during the preparation of ethylene-propylene by catalytically cracking naphtha. The present invention uses the composition having the chemical formula (on the basis of the atom ratio): A a B b P c O x , so as to magnificently solve said problems. The present invention therefore can be industrially used to produce ethylene and propylene by catalytically cracking naphtha.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. Ser. No. 12/063,598, filed Sep. 9, 2008, which is the U.S. National Phase of PCT/CN2006/002072, filed Aug. 15, 2006, which claims the benefit of Chinese patent application No. 200510028794.3, filed Aug. 15, 2005, each incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a catalyst for catalytic cracking fluidized-bed, especially a catalyst for fluidized-bed to produce ethylene-propylene by catalytically cracking naphtha.

BACKGROUND ART

Currently, the primary process for producing ethylene-propylene is the steam pyrolysis, and the commonly used materials are naphtha. However, there are several shortcomings for steam pyrolysis of naphtha, e.g. high reaction temperature, rigorous technological conditions, high requirements on the devices, particularly on the furnace tube materials, and high-loss. Various meaningful studies thus are carried out. Catalytic cracking is the most attracting and promising one, and the object thereof is to find a suitable cracking catalyst to increase the selectivity of ethylene-propylene, decrease the reaction temperature and have some certain flexibility of the ethylene-propylene yield.

From the current documents, most catalytic cracking researchers generally use the molecular sieves having a high silica alumina ratio as the catalytic materials and use high valent metallic ions for exchanging and impregnating. However, the molecular sieves have a worse hydrothermal stability and are difficult to regenerate.

U.S. Pat. No. 6,211,104 and CN1504540A disclosed a catalyst comprising 10-70 wt % of clay, 5-85 wt % of inorganic oxides and 1-50 wt % of molecular sieves. Various materials for the conventional steam pyrolysis therein exhibited excellent activity stability and high yields of light olefin, especially ethylene, wherein said molecular sieves were produced by impregnating 0-25 wt % of Y type zeolite having a high silica alumina ratio or ZSM molecular sieves having MFI structure with phosphorus/alumina, magnesium or calcium, and were substantially the pure molecular sift catalysts.

In addition, oxides are also used as catalysts.

U.S. Pat. No. 4,620,051 and U.S. Pat. No. 4,705,769 of PHILLIPS PETROLEUM CO (US) disclosed using the oxide catalyst having manganese oxide and iron oxide as active ingredients and added with rare earth element La and alkaline earth metal Mg to crack C₃ and C₄ materials. Under the circumstance that Mn,Mg/Al₂O₃ catalyst was placed in the fixed-bed reactor in the laboratory, water and butane are in a molar ratio of 1:1 at a temperature of 700° C.; the butane conversion rate may achieve 80%; and ethylene and propylene had the selectivity of 34% and 20% respectively. Said patents also alleged that naphtha and fluidized-bed reactors could be used therein.

CN1317546A of ENICHEM SPA (IT) disclosed a steam cracking catalyst having the chemical formula of 12CaO.7Al₂O₃. Naphtha may be used as the raw materials. The reaction was carried out at a temperature of 720-800° C. and under 1.1-1.8 atmospheric pressure, and the contact time was 0.07-0.2 s. The yield of ethylene and propylene may achieve 43%.

USSR Pat1298240.1987 disclosed feeding Zr₂O₃ and potassium vanadate loaded on pumice or ceramic into a medium-size apparatus having a temperature of 660-780° C. and a space velocity of 2-5 hour⁻¹, wherein the weight ratio of water/straight-run gasoline may be 1:1. The normal alkane C₇₋₁₇, cyclohexane and straight-run gasoline were used as the raw materials, wherein the ethylene yield could achieve 46%, and propylene 8.8%.

CN1480255A introduced an oxide catalyst for producing ethylene-propylene by catalytically cracking naphtha as the raw materials at a temperature of 780° C., wherein the ethylene-propylene yield may achieve 47%.

Naphtha further contains a part of components having different molecular diameters and different cracking performances, such as aromatic hydrocarbons, cyclanes and the like. The molecular sieves shall have a better selectivity to ethylene and propylene so as to crack these complex raw materials into ethylene and propylene. In order to reduce coking and decrease the partial pressure of the raw materials, the catalytic cracking should be generally carried out in the environment in which water vapor is present. In addition, the catalyst needs to have a better hydrothermal stability and can be regenerated repeatedly.

Since the molecular sieves such as ZSM-5 molecular sieves, Y zeolites and Mordenitee (MOR) have better shape selective catalytic performances and thermal stability, they are widely used in the petrochemical field. These molecular sieves have a homogeneous pore diameter and have different catalytic performances for the same reactants, so that the separate application thereof is disadvantageous to the processing of raw materials having complex ingredients.

The mechanical mixtures containing these two molecular sieves have multistage pore diameters, and the catalytic performances of the ingredients are different from each other. Thus, when the complex feedstocks having different molecular diameters are processed, the respective catalytic effects of said ingredients can be exerted so as to show better catalytic performances than the single ingredient. However, the mechanical mixtures merely involve the simple mixing of two molecular sieves, and their acid amount and acid strength are also the simple addition of two ingredients. Moreover, their pore diameters do not affect each other; their catalytic effects are separated from each other; the catalytic reaction is finished within each molecular sieve.

In conclusion, molecular sieves as the primary cracking catalysts are attached great importance. However, the examples regarding the co-grown molecular sieves mixing with oxides are rarely reported.

CONTENTS OF THE INVENTION

The technical problems to be solved by the present invention are high reaction temperature, low cryogenic activity of catalysts and worse selectivity during the preparation of ethylene-propylene by catalytic cracking in the prior art, and to provide a novel catalyst for catalytic cracking fluidized-bed. Said catalyst is used to produce ethylene-propylene by catalytically cracking naphtha, which not only decreases the catalytic cracking temperature, but also enhances the selectivity of the catalyst.

In order to solve the problems above, the present invention carries out the technical solution of a catalyst for catalytic cracking fluidized-bed, comprising a support and a composition having the following chemical formula, which is on the basis of atom ratio:

A_(a)B_(b)P_(c)O_(x),

wherein A therein is at least one selected from the group consisting of rare earth elements;

B is at least one element selected from the group consisting of VIII, IB, IIB, VIIB, VIB, IA and IIA;

a ranges from 0.01-0.5;

b ranges from 0.01-0.5;

c ranges from 0.01-0.5; and

X is the total number of oxygen atoms satisfying the requirements on the valence of each of the elements in the catalyst;

Wherein the support is composite molecular sieves or a mixture of composite molecular sieves and at least one selected from the group consisting of SiO₂ and Al₂O₃, and

said composite molecular sieves are the composite co-grown by at least two molecular sieves selected from the group consisting of ZSM-5, Y zeolite, β zeolite, MCM-22, SAPO-34 and mordenitee, wherein the molecular sieves in the catalyst are in an amount of 0-60% by weight of the catalyst.

In the technical solution above, a preferably ranges from 0.01-0.3; b preferably ranges from 0.01-0.3; c preferably ranges from 0.01-0.3. The preferred rare earth element is at least one selected from the group consisting of La and Ce; the preferred VIII group element is at least one selected from the group consisting of Fe, Co and Ni; the preferred IB is at least one selected from the group consisting of Cu and Ag; the preferred IIB is Zn; the preferred VIIB is Mn; the preferred VIB is selected from the group consisting of Cr, Mo and mixtures thereof; the preferred IA is at least one selected from the group consisting of Li, Na and K; and the preferred IIA is at least one selected from the group consisting of Ma, Ca, Ba and Sr. The preferred molecular sift is at least one selected from the group consisting of ZSM-5, Y zeolite, mordenite and β zeolite; and the composite molecular sift is at least one selected from the group consisting of ZSM-5/mordenite, ZSM-5/Y zeolite and ZSM-5/β zeolite. The silica alumina molar ratio SiO₂/Al₂O₃ of molecular sieves and composite molecular sieves preferably ranges from 10-500, more preferably 20-300. In the catalyst, the molecular sieves are in an amount of 10-60% by weight, preferably 20-50% by weight of the catalyst.

The catalyst for catalytic cracking fluidized-bed of the present invention is used to catalytically crack heavy oil, light diesel oil, light gasoline, catalytically cracked gasoline, gas oil, condensate oil, C4 olefin or C5 olefin.

During the preparation of the catalyst for catalytic cracking fluidized-bed of the present invention, the elements A in the raw materials are the corresponding nitrates, oxalates or oxides; the elements B are the corresponding nitrates, oxalates, acetates or soluble halides; and the phosphorus element used therein is derived from phosphoric acid, triammonium phosphate, diammonium phosphate and ammonium dihydrogen phosphate.

In the preparation of the catalyst, active elements may be impregnated onto the molecular sieves, or homogeneously mixed with molecular sieves for moulding. The preparation of the moulding form of the catalyst comprises heating and reflowing the slurry added with various ingredient elements and supports in a water bath having a temperature of 70-80° C. for 5 hours and spray-drying. The resulted powder is then calcined in the muffle furnace at a temperature of 600-750° C. for 3-10 hours.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIG. 1 is a XRD diffraction pattern of a ZSM-5/β zeolite co-grown molecular sieves;

The FIG. 2 is a SEM photograph of a composite molecular sieve co-grown by ZSM-5/Mordenitee molecular sieve; and

The FIG. 3 is a NH3-TPD spectra of a co-growth ZSM-5/MOR composite molecular sieve and a physical mixture of ZSM-5 and MOR

DETAILED DESCRIPTION

Since the porous co-grown materials are greatly different from the simple phase mechanical mixture in the surface and interface, acidity and specific surface, and have a great acid amount and a stronger acidity, the strong acid amount and weak acid amount of the co-grown molecular sieves both are notably higher than those of the mechanical mixture of the phase contained therein. This is because there appears a phase interface between ZSM-5 and MOR when the solid-state phase transition occurs. Since said ZSM-5 and MOR have different crystal cell parameters, they are not completely coherent so as to produce a certain distortion energy on the phase interface. Due to the great charge density at the position of the distortion energy so as to have adsorptivity and produce a certain acidity, the co-grown molecular sieves obtained during the crystal-transforming process have a greater than acid amount than the corresponding mechanical mixtures. The co-grown molecular sieves have multistage channels so as to have better catalytic performances, and can be used for processing the raw material mixtures having different molecular diameters.

The FIG. 2 shows a SEM photograph of a composite molecular sieve co-grown by ZSM-5/Mordenitee molecular sieve. Therein the ball-like structures are ZSM-5 molecular sieve and the bar-shape structures are Mordenitee (MOR) molecular sieve. It can be seen that the two types of structures are tightly interlaced with each other and have a distinct phase interface, i.e., an interface between two phases of different type molecular sieve. This may due to a mosaictype growth of the microcrystallites in the composite molecular sieve.

In comparison, the particles of the different types of molecular sieves in a physical mixture would be separately dispersed. That is to say, like a pile of toy bricks with different shapes, the particles of the different types of molecular sieves can be stacked loosely and randomly, but would not be interlaced so tightly. The phase interface would be unlikely produced in a physical mixture.

This difference can also be seen in the FIG. 3, which is a NH3-TPD spectra of a co-growth ZSM-5/MOR composite molecular sieve and a physical mixture of ZSM-5 and MOR. The FIG. 3 shows that the integral area of the co-grown composite is significantly larger than that of the physical mixture. This illustrates that the acid amount of the co-grown composite is larger than acid amount of the physical mixture. The increase of acid amount should be produced by the increased negative charge density at the phase interface caused by the lattice distortion, that is to say, the relative aggregation of the negative charge at the phase interface forms a Lewis acid.

As compared with the corresponding mechanical mixtures, the co-grown molecular sieves containing such two ingredients have not only the multistage channel effect, but also stronger acidity. Moreover, since the co-grown molecular sieves are formed by partially crystal-transforming one ingredient, the channels of two ingredients of the co-grown molecular sieves communicate with each other, so as to better exert their synergistic catalytic performances.

For example, it is reported according to the inventor's M A Guangwei et al, Synthesizing Mechanism II of ZSM-5/MOR Co-grown Molecular Sieves—Phase transition during the synthesis, Journal of the Chinese Ceramic Society, 2010, 38(10) 1937-1943, that there is the phase transition process during the synthesis of the co-grown molecular sieves. During such process, lattice distortion occurs since the crystal lattices of two phases do not match, so as to resulting an increased acid amount and a strengthened acidity of the co-grown molecular sieves.

Thus the co-grown molecular sieves can be used for processing the complex ingredients having different molecular diameters and can really exert their synergistic catalytic effects since they have a multistage channel structure, a great acid amount and a widely distributed strong acid and weak acid scope.

Since at least one selected from the group of SiO₂, Al₂O₃, molecular sieves or composite molecular sieves having acidity, shape selectivity and high specific surface area is used as the cracking auxiliary agent, it is advantageous to cracking olefin materials according to the carbonium ion mechanism, producing low carbon olefins, and obtaining the synergistic effects when being compounded with active ingredients having oxidation reduction. At a relatively low temperature (580-650° C.), it achieves better catalytically cracking effects, obtains relatively high ethylene-propylene yield and better technical effects.

MODE OF CARRYING OUT THE INVENTION

In order to evaluate the activity of the catalyst of the present invention, naphtha is used as the raw material (see Table 1 for specific indexes). The reaction is carried out at a temperature of 580-650° C., a catalyst loading of 0.5-2 g naphtha/g catalyst·h, and a water/naphtha weight ratio of 0.5-3:1. The fluidized-bed reactor has an inner diameter of 39 mm and a reaction pressure of 0-0.2 MPa.

TABLE 1 Indexes of naphtha raw material Items Data Density (20° C.) kg/m3 704.6 Distillation range, initial distillation 40 range, ° C. Final distillation range, ° C. 60 Saturated steam pressure (20° C.) kpa 50.2 Alkane % (by weight) 65.2 Normal Alkane % 32.5 Cyelane % 28.4 Olefin % (by weight) 0.17 Arene % (by weight) 6.2

The present invention is further elucidated via the following examples.

EXAMPLE 1

2 g of ammonium nitrate was dissolved into 100 ml of water, and 20 g of ZSM-5 molecular sieves row powder (having a silica alumina molar ratio SiO₂/Al₂O₃ of 400) was added therein. After the exchange for 2 hours at 90° C., the filtration was carried out to obtain the filter cake.

16.2 g of ferric nitrate, 7.86 g of cobalt nitrate, 12.23 g of chromic nitrate and 2.4 g of lanthanum nitrate were dissolved into 250 ml of water to obtain the solution A. 4.65 g of diammonium phosphate was dissolved into 100 ml of water and then added into the solution A, to obtain the slurry B after homogeneous stirring.

The slurry B was heated in a water bath having a temperature of 70-80° C., and 15 g of molecular sieves after exchange and 5 g of silicon dioxide were added therein. After refluxing for 5 hours, the slurry was dried and moulded by a spray-drying apparatus.

The dried powder was heated in the muffle furnace at a temperature of 740° C. and ignited for 5 hours, to obtain a catalyst after cooling. The catalyst was then passed through the sift having 100 meshes.

The chemical formula of the catalyst, Fe_(0.11)Co_(0.08)Cr_(0.08)La_(0.04)P_(0.05)O_(x)+Support 31.57 wt. %, was obtained.

The catalyst activity was evaluated under the following conditions: a fluidized-bed reactor having 39 mm inner diameter, a reaction temperature of 650° C. and a pressure of 0.15 MPa. The water/naphtha weight ratio was 3:1; the catalyst loading amount was 20 g; and the loading was 1 g of naphtha/g catalyst·hour. The gaseous product was collected to carry out the gas phase chromatographic analysis, wherein the product distribution and the ethylene+propylene yield were shown in Table 2.

TABLE 2 Gas phase product distribution and ethylene + propylene yield Content (vol % for H₂, Products and wt % for the balance) H₂ (vol %) 15.5 Methane 17.08 Ethane 1.62 Ethylene 42.23 Propane 0.41 Propylene 14.72 C₄ 7.98 the balance 15.96 Conversion rate 76.37 Ethylene yield 32.25 Propylene yield 11.24 Ethylene + propylene yield 43.49

EXAMPLE 2

2 g of ammonium nitrate was dissolved into 100 ml of water, and 20 g of Y molecular sieves raw powder (having a silica alumina molar ratio SiO₂/Al₂O₃ of 20) was added therein. After the exchange for 2 hours at 90° C., the filtration was carried out to obtain the filter cake.

7.27 g of nickel nitrate, 8.48 g of chromic nitrate and 5.44 g of cerous nitrate were dissolved into 250 ml of water to obtain the solution A. 6.54 g of diammonium phosphate was dissolved into 100 ml of water and then added into the solution A, to obtain the slurry B after homogeneous stirring.

15 g of molecular sieves after exchange, 5 g of silicon dioxide and 2 g of alumina were added into the slurry B. The remaining was the same as Example 1 to obtain the chemical formula of the catalyst, Ni_(0.07)Cr_(0.06)Ce_(0.09)P_(0.08)O_(x)+Support 44.9 wt. %.

The catalyst evaluation was the same as Example 1, and the cracked product distribution and the ethylene+propylene yield were shown in Table 3.

TABLE 3 Gas phase product distribution and ethylene + propylene yield Content (vol % for H₂, Products and wt % for the balance) H₂ (vol %) 15.52 Methane 20.46 Ethane 2.40 Ethylene 44.00 Propane 0.37 Propylene 14.28 C₄ 5.60 the balance 12.89 Conversion rate 75.26 Ethylene yield 33.11 Propylene yield 10.75 Ethylene + propylene yield 43.86

EXAMPLE 3

5.49 g of cobalt nitrate, 5.60 g of zinc nitrate, 5.44 g of cerous nitrate, 6.30 g of copper nitrate were dissolved into 250 ml of water to obtain the solution A. 6.54 g of diammonium phosphate was dissolved into 100 ml of water and then added into the solution A, to obtain the slurry B after homogeneous stirring.

10 g of hydrogen-type ZSM-5 molecular sieves having a silica alumina ratio of 120, 5 g of hydrogen-type β zeolite having a silica alumina ratio of 30 and 5 g of silicon dioxide were added into the slurry B. The remaining was the same as Example 1 to obtain the chemical formula of the catalyst, Co_(0.06)Zn_(0.06)Cu_(0.08)Ce_(0.09)P_(0.08)O_(x)+Support 40.5 wt. %.

The product yield was shown in Table 4.

EXAMPLE 4

7.62 g of ferric nitrate, 5.60 g of zinc nitrate, 5.44 g of cerous nitrate, 5.18 g of calcium nitrate were dissolved into 250 ml of water to obtain the solution A. 6.54 g of diammonium phosphate was dissolved into 100 ml of water and then added into the solution A, to obtain the slurry B after homogeneous stirring.

5 g of hydrogen-type mordenitee having a silica alumina ratio of 20, 5 g of hydrogen-type MCM-22 having a silica alumina ratio of 40, 22.5 g of hydrogen-type β zeolite having a silica alumina ratio of 30 and 5 g of silicon dioxide were added to the solution. The remaining was the same as Example 1 to obtain the chemical formula of the catalyst, Fe_(0.05)Zn_(0.06)Ce_(0.09)Ca_(0.04)P_(0.08)O_(x)+Support 39.7 wt. %.

The product yield was shown in Table 4.

EXAMPLE 5

5.49 g of cobalt nitrate, 10.81 g of 50% manganous nitrate solution and 5.44 g of cerous nitrate were dissolved into 250 ml of water to obtain the solution A. 6.54 g of diammonium phosphate was dissolved into 100 ml of water and then added into the solution A, to obtain the slurry B after homogeneous stirring.

20 g of alumina was added to the slurry B, and the remaining was the same as Example 1 to obtain the chemical formula of the catalyst, Mn_(0.08)Co_(0.06)Ce_(0.09)P_(0.08)O_(x)+Support 46.6 wt. %.

The product yield was shown in Table 4.

EXAMPLE 6

5.49 g of cobalt nitrate, 10.81 g of 50% manganous nitrate solution and 5.44 g of cerous nitrate were dissolved into 250 ml of water to obtain the solution A. 6.54 g of diammonium phosphate was dissolved into 100 ml of water and then added into the solution A, to obtain the slurry B after homogeneous stirring.

20 g of silicon dioxide was added to the slurry B, and the remaining was the same as Example 1 to obtain the chemical formula of the catalyst, Mn_(0.08)Co_(0.06)Ce_(0.09)P_(0.08)O_(x)+Support 46.6 wt. %.

The product yield was shown in Table 4.

EXAMPLE 7

5.49 g of cobalt nitrate, 8.48 g of chromic nitrate, 5.44 g of cerous nitrate and 1.1 g of potassium nitrate were dissolved into 250 ml of water to obtain the solution A. 6.54 g of diammonium phosphate was dissolved into 100 ml of water and then added into the solution A, to obtain the slurry B after homogeneous stirring.

15 g of silica and 5 g of alumina as the support were added to the slurry B, and the remaining was the same as Example 1 to obtain the chemical formula of the catalyst, Co_(0.06)Cr_(0.06)Ce_(0.09)K_(0.02)P_(0.08)O_(x)+45.1 wt. % Support (containing no molecular sieves).

The product yield was shown in Table 4.

TABLE 4 Product yield of different supports Ethylene Propylene Ethylene + Examples yield yield propylene yield Example 3 36.0% 5.47% 41.47% Example 4 25.37% 15.35% 40.72% Example 5 30.71% 9.33% 40.04% Example 6 26.98% 12.49% 39.47% Example 7 27.12% 12.33% 39.45%

EXAMPLE 8

The slurry B was prepared according to the process in Example 1. The same ZSM-5 molecular sieves and silicon dioxide were added directly without any loading process. After homogeneous stirring, the slurry B was directly moulded by spraying. The composition of the catalyst was the same as that in Example 1. Then the evaluation was carried out according to the process of Example 1, and the results were shown in Table 5.

EXAMPLE 9

284 g of sodium metasilicate was dissolved into 300 g of distilled water to obtain the solution A. 33.3 g of aluminium sulphate and 100 g of distilled water were prepared into the solution B. The solution B was slowly poured into the solution A and strongly stirred. Then 24.4 g of ethylene diamine was added, and the pH thereof was adjusted to 11.5 with weak sulphuric acid after stirring for a period of time. The molar proportion of the sol was controlled to be Si:Al:ethylene diamine:H₂O=1:0.1:0.4:40. The mixed solutions were fed into the autoclave, thermally insulated at 180° C. for 40 hours, taken out, washed with water, dried and calcined to obtain composite molecular sieves of ZSM-5 and mordenitee. Said composite molecular sieves were exchanged twice at 70° C. with 5% ammonium nitrate solution and then calcined. Said process was repeated twice to obtain the hydrogen-type ZSM-5/mordenitee composite molecular sieves.

The slurry B was prepared according to the process in Example 1. ZSM-5/mordenitee composite molecular sieves having a silica alumina ratio of 20 and silicon dioxide in the same amount were added therein, and the same process was used to prepare a catalyst. Then the evaluation was carried out according to the process of Example 1, and the results were shown in Table 5.

EXAMPLE 10

284 g of sodium metasilicate was dissolved into 300 g of distilled water to obtain the solution A. 33.3 g of aluminium sulphate and 100 g of distilled water were prepared into the solution B. The solution B was slowly poured into the solution A and strongly stirred. Then 24.4 g of ethylene diamine was added, and the pH thereof was adjusted to 11 with weak sulphuric acid after stirring for a period of time. 5 g of Y zeolite crystal seeds were added therein, and the molar proportion of the sol was controlled to be Si:Al:ethylene diamine:H₂O=1:0.1:0.4:40. The mixed solutions were fed into the autoclave, thermally insulated at 170° C. for 36 hours, taken out, washed with water, dried and calcined to obtain composite molecular sieves of ZSM-5 and Y zeolite. Said composite molecular sieves were exchanged twice at 70° C. with 5% ammonium nitrate solution and then calcined. Said process was repeated twice to obtain the hydrogen-type ZSM-5/Y zeolite composite molecular sieves.

The slurry B was prepared according to the process in Example 1. ZSM-5/Y zeolite composite molecular sieves having a silica alumina ratio of 20 and silicon dioxide in the same amount were added therein, and the same process was used to prepare a catalyst. Then the evaluation was carried out according to the process of Example 1, and the results were shown in Table 5.

EXAMPLE 11

284 g of sodium metasilicate was dissolved into 300 g of distilled water to obtain the solution A. 33.3 g of aluminium sulphate and 100 g of distilled water were prepared into the solution B. The solution B was slowly poured into the solution A and strongly stirred. Then 24.4 g of ethylene diamine and 10 g of tetraethyl ammonium hydroxide were added, and the pH thereof was adjusted to 12 with weak sulphuric acid after stirring for a period of time. 5 g of β zeolite crystal seeds were added, and the molar proportion of the sol was controlled to be Si:Al:ethylene diamine:H₂O=1:0.1:0.4:40. The mixed solutions were fed into the autoclave, thermally insulated at 160° C. for 40 hours, taken out, washed with water, dried and calcined to obtain composite molecular sieves of mordenitee and β zeolite. Said composite molecular sieves were exchanged twice at 70° C. with 5% ammonium nitrate solution and then calcined. Said process was repeated twice to obtain the hydrogen-type mordenitee/β zeolite composite molecular sieves.

The slurry B was prepared according to the process in Example 1. β zeolite/mordenitee composite molecular sieves having a silica alumina ratio of 20 and silicon dioxide in the same amount were added therein, and the same process was used to prepare a catalyst. Then the evaluation was carried out according to the process of Example 1, and the results were shown in Table 5.

EXAMPLE 12

The slurry B was prepared according to the process in Example 1. 5 g of the hydrogen type ZSM-5 having a silica alumina ratio of 120, 10 g of ZSM-5/mordenitee composite molecular sieves having a silica alumina ratio of 20, 5 g of silicon dioxide were added therein, and the same process was used to prepare a catalyst. Then the evaluation was carried out according to the process of Example 1, and the results were shown in Table 5.

EXAMPLE 13

The slurry B was prepared according to the process in Example 1. 12 g of the hydrogen type ZSM-5 having a silica alumina ratio of 150 as a support was added therein to obtain a catalyst having the composition chemical formula of Fe_(0.11)Co_(0.08)Cr_(0.08)La_(0.04)P_(0.05)O_(x)+Support 21.32 wt. %. Then the evaluation was carried out according to the process of Example 1, and the results were shown in Table 5.

EXAMPLE 14

The slurry B was prepared according to the process in Example 1. 20 g of the hydrogen type ZSM-5/mordenitee having a silica alumina ratio of 30 as a support was added therein to obtain a catalyst having the composition chemical formula of Fe_(0.11)Co_(0.08)Cr_(0.08)La_(0.04)P_(0.05)O_(x)+Support 31.6 wt. %. Then the evaluation was carried out according to the process of Example 1, and the results were shown in Table 5.

TABLE 5 Ethylene Propylene Ethylene + Examples yield yield propylene yield Example 8 32.36% 11.17% 43.53% Example 9 33.76% 11.45% 45.21% Example 10 33.42% 10.83% 44.25% Example 11 32.72% 10.87% 43.59% Example 12 33.47% 11.21% 44.68% Example 13 34.52% 12.07% 46.59% Example 14 35.02% 12.53% 47.55%

EXAMPLE 15

Under the same conditions as those in Example 1, the evaluation was carried out by using the catalyst prepared according to Example 1 and the light diesel oil having a boiling point of lower than 350° C. as the reaction materials, and the results were shown in Table 6.

EXAMPLE 16

Under the same conditions of 550° C., a water/oil ratio of 3:1 and a space velocity of 1 as those in Example 1, the evaluation was carried out by using the catalyst prepared according to Example 1 and the mixed C4 (alkane:olefin=1:1) as the reaction materials, and the results were shown in Table 6.

TABLE 6 Ethylene Propylene Ethylene + Examples yield yield propylene yield Example 15 28.47% 9.25% 37.72% Example 16 12.21% 38.63% 50.84%

EXAMPLE 17

According to the process in Example 1, a catalyst was prepared by using the hydrogen type ZSM-5/mordenitee as the support prepared in Example 9, and introduced into the fixed-bed reactor having an inner diameter of 12 mm. The reaction was carried out under the conditions of a reaction temperature of 650° C., a mass space velocity of 2 hour⁻¹ and a water/raw oil mass ratio of 1.5, and the results were shown in Table 7.

EXAMPLE 18

According to the process in Example 1, a catalyst was prepared by using the hydrogen type ZSM-5/Y zeolite as the support prepared in Example 10. The evaluation was carried out according to Example 17, and the results were shown in Table 7.

EXAMPLE 19

According to the process in Example 1, a catalyst was prepared by using the hydrogen type β zeolite/mordenitee as the support prepared in Example 11. The evaluation was carried out according to Example 17, and the results were shown in Table 7.

EXAMPLE 20

284 g of sodium metasilicate was dissolved into 300 g of distilled water to obtain the solution A. 16.7 g of aluminium sulphate and 100 g of distilled water were prepared into the solution B. The solution B was slowly poured into the solution A and strongly stirred. Then 12.2 g of ethylene diamine and 29.4 g of tetraethyl ammonium hydroxide (the mixed template agent was labeled as M) were added, and the pH thereof was adjusted to 11 with weak sulphuric acid after stirring for a period of time. The molar proportion of the sol was controlled to be Si:Al:M:H₂O=1:0.05:0.4:40, and 2.8 g of β zeolite crystal seeds were added. The mixed solutions were fed into the autoclave, thermally insulated at 160° C. for 40 hours, taken out, washed with water, dried and calcined to obtain co-grown molecular sieves of ZSM-5/β zeolite. Said composite molecular sieves were exchanged twice at 70° C. with 5% ammonium nitrate solution and then calcined. Said process was repeated twice to obtain the hydrogen-type ZSM-5/β zeolite co-grown molecular sieves.

According to the process in Example 1, a catalyst was prepared by using as the support the hydrogen type ZSM-5/β zeolite prepared above. The evaluation was carried out according to Example 17, and the results were shown in Table 7.

TABLE 7 Ethylene Propylene Ethylene + propylene Examples yield (wt. %) yield (wt. %) yield (wt. %) Example 17 32.01 30.94 62.95 Example 18 28.1 33.35 61.45 Example 19 29.06 32.12 61.18 Example 20 31.15 31.08 62.23

EXAMPLES 21-22

According to the method and contents as stated in Example 9, the addition amount of sodium metaaluminate was respectively changed to 66.6 g and 16.0 g, and the molar proportion of other materials remained unchanged. The pH value of two solutions was adjusted to be 13.5 and 11 respectively, and other conditions and steps remained unchanged to prepare the ZSM-5/mordenitee composite (co-grown) molecular sieves provided in the present invention and labeled respectively as H-2 and H-3. The physical property indexes of the composite molecular sieves measured by XRD and SEM are shown in Table 8. The reviewing of the catalyst was carried out according to the method as stated in Example 12, and the results are shown in Table 9.

EXAMPLES 23-24

According to the method and contents as stated in Example 9, the hydrothermal temperature was changed to 200° C., 160° C. and 120° C. respectively, and other conditions and steps remained unchanged to prepare the ZSM-5/mordenitee co-grown molecular sieves provided in the present invention and labeled respectively as H-6, H-7 and H-8. The physical property indexes of the composite molecular sieves measured by XRD and SEM are shown in Table 8. The reviewing of the catalyst was carried out according to the method as stated in Example 12, and the results are shown in Table 9.

TABLE 8 Physical property indexes of ZSM-5/mordenitee composite molecular sieves Average crystal grain diameter ZSM-5 content Mordenitee Samples (micrometer) (wt %) content (wt %) H2 6 58.5 41.5 H3 3 94.5 5.5 H4 5 85.0 15.0 H5 2 95.5 4.5 H6 0.5 97.0 3.0

TABLE 9 Catalytic performances of ZSM-5/mordenitee composite molecular sieves Total yield of Ethylene Propylene ethylene and Samples yield (wt %) yield (wt %) propylene (wt %) H3 30.45 13.27 43.72 H4 29.07 16.59 45.66 H5 25.53 17.14 42.67 H6 28.24 16.03 44.27 H7 25.76 16.40 42.16

EXAMPLE 25

284 g of sodium metasilicate were dissolved in 300 g of distilled water to form the solution A; 5.56 g of aluminium sulphate and 100 g of distilled water were used to produce the solution B. The solution B was slowly dropped into the solution A, and the mixed solution was strongly stirred. 12.2 g of ethylene diamine and 29.4 g of tetraethyl ammonium hydroxide were added (the mixed template agent labeled as M). After stirring for a period of time, the pH thereof was adjusted to 11 with dilute sulfuric acid. The molar proportion of the sol was controlled to be Si:Al:M:H₂O=1:0.0167:0.4:40, and 2.8 g of β zeolite crystal seed was added. The mixed solution was fed into the autoclave, thermally insulated at 160° C. for 40 h, taken out and washed with water twice, dried at 120° C. for 4 h, calcinated at 550° C. for 3 h, to produce ZSM-5/β zeolite co-grown molecular sieves. The XRD diffraction patter is shown in the Curve 1 of FIG. 1. According to the XRD diffraction quantification, it can be seen that ZSM-5 in the co-grown molecular sieves was in an amount of 94.6% by weight; and β zeolite was in an amount of 5.4% by weight. After exchanging twice at 70° C. with ammonium nitrate solution having a concentration of 5%, and calcining at 550° C. for 3 h, repeating the aforesaid operations twice, the hydrogen-type ZSM-5/β zeolite co-grown molecular sieves were produced and labeled as FH-1. The ratio of ZSM-5 and β zeolite is shown in Table 10. According to the method as stated in Example 1, the catalyst was prepared and reviewed under the conditions as stated in Example 1, and the results are shown in Table 11.

EXAMPLES 26-27

According to the method as stated in Example 25, the pH value of the solution was controlled to be 10.5 and 11.5 respectively to synthesize ZSM-5/β zeolite co-grown molecular sieves labeled respectively as FH-2 and FH-3. The ratio of ZSM-5 and β zeolite is shown in Table 9. The reviewing was carried out according to the method as stated in Example 1, and the results are shown in Table 11.

EXAMPLES 28-29

According to the method as stated in Example 25, the molar proportion of the solution was controlled to be the same, and 5.68 g and 11.3 g of β zeolite crystal seeds were respectively added therein to synthesize ZSM-5/β zeolite co-grown molecular sieves labeled respectively as FH-4 and FH-5. The ratio of ZSM-5 and β zeolite was measured by the XRD diffraction pattern, and the results are shown in Table 10. The reviewing was carried out according to the method as stated in Example 1, and the results are shown in Table 11.

EXAMPLES 30-31

According to the method as stated in Example 25, the molar proportion of the solution was controlled to be the same, and the crystallization temperatures were respectively set up to be 150° C. and 170° C. to synthesize ZSM-5/β zeolite co-grown molecular sieves labeled respectively as FH-6 and FH-7, wherein the ratio of ZSM-5 and β zeolite is shown in Table 10. The reviewing was carried out according to the method as stated in Example 1, and the results are shown in Table 11.

TABLE 10 Sample No. ZSM-5 ratio (wt %) β zeolite ratio (wt %) FH-1 94.5 5.5 FH-2 92.5 7.5 FH-3 96.5 3.5 FH-4 86.4 13.6 FH-5 90.0 10.0 FH-6 80.5 19.5 FH-7 91.0 9.0

TABLE 11 Ethylene Propylene Total Sample No. yield (wt %) yield (wt %) yield (wt %) FH-1 28.47 17.25 45.72 FH-2 26.25 17.53 43.78 FH-3 29.11 17.83 46.94 FH-4 28.54 17.37 45.91 FH-5 27.06 19.32 46.38 FH-6 27.52 16.12 43.64 FH-7 28.57 17.73 46.30

EXAMPLES 32-35

The co-grown molecular sieves synthesized according to Examples 9, 10, 11 and 25 were taken to produce the hydrogen-type co-grown molecular sieves according to the method as stated in Example 25. The desorption curve of ammonia was determined by the Temperature Programmed Desorption (TPD) device, and the desorption temperatures at strong and weak sites were used to represent the acid strength. The desorbed ammonia passed through chromatogram, was absorbed with excessive dilute sulfuric acid, and backtitrated with the standard solution of sodium hydroxide, so as to calculate the acid amount of the molecular sieves to be measured. The results are shown in Table 5.

COMPARISON EXAMPLE 1

The acidity of ZSM-5 molecular sieves having a silica alumina ratio of 20 was measured according to the method as stated in Example 32, and the results are as shown in Table 12.

COMPARISON EXAMPLE 2

The acidity of mordenitee molecular sieves having a silica alumina ratio of 20 was measured according to the method as stated in Example 32, and the results are as shown in Table 12.

COMPARISON EXAMPLE 3

The acidity of Y zeolite molecular sieves having a silica alumina ratio of 10 was measured according to the method as stated in Example 32, and the results are as shown in Table 12.

COMPARISON EXAMPLE 4

ZSM-5 molecular sieves having a silica alumina ratio of 20 and mordenitee molecular sieves were used to prepare the mechanical mixtures according to the mass percentage content of 85% by mass of ZSM-5 and 15% by mass of mordenitees. The acidity thereof was measured according to the method as stated in Example 32, and the results are as shown in Table 12. The catalytic performance of the mechanical mixtures was reviewed according to the manner in Example 1, and the results are as shown in Table 13.

COMPARISON EXAMPLE 5

ZSM-5 molecular sieves having a silica alumina ratio of 20 and Y zeolites having a silica alumina ratio of 10 were used to prepare the mechanical mixtures according to the mass percentage content of 80% by mass of ZSM-5 and 20% by mass of β zeolites. The acidity thereof was measured according to the method as stated in Example 32, and the results are as shown in Table 12. The catalytic performance of the mechanical mixtures was reviewed according to the manner in Example 1, and the results are as shown in Table 13.

COMPARISON EXAMPLE 6

ZSM-5 molecular sieves having a silica alumina ratio of 20 and β zeolites having a silica alumina ratio of 20 were used to prepare the mechanical mixtures according to the mass percentage content of 80.5% by mass of ZSM-5 and 19.5% by mass of β zeolites. The acidity thereof was measured according to the method as stated in Example 32, and the results are as shown in Table 12. The catalytic performance of the mechanical mixtures was reviewed according to the manner in Example 1, and the results are as shown in Table 13.

COMPARISON EXAMPLE 7

Mordenitees having a silica alumina ratio of 20 and β zeolites having a silica alumina ratio of 20 were used to prepare the mechanical mixtures according to the mass percentage content of 60.0% by mass of ZSM-5 and 40.0% by mass of β zeolites. The acidity thereof was measured according to the method as stated in Example 32, and the results are as shown in Table 12. The catalytic performance of the mechanical mixtures was reviewed according to the manner in Example 1, and the results are as shown in Table 13.

TABLE 12 Examples or Desorption Desorption Acid amount Comp. Molecular temperature at weak temperature at (×10⁻⁴ Examples sieve type acid site (° C.) strong acid site (° C.) mole/g) Example 32 ZSM-5/MOR 302 498 12.02 Example 33 ZSM-5/Y zeolites 281 490 11.34 Example 34 MOR/β zeolites 240 510 11.00 Example 35 ZSM-5/β zeolites 250 450 9.50 Comp. Ex. 1 ZSM-5 245 420 5.53 Comp. Ex. 2 MOR 250 510 8.06 Comp. Ex. 3 Y zeolites 230 420 4.50 Comp. Ex. 4 β zeolites 240 480 5.34 Comp. Ex. 5 ZSM-5, MOR 260 490 6.10 mechanical mixtures Comp. Ex. 6 ZSM-5, Y zeolite 240 450 5.40 mechanical mixtures Comp. Ex. 7 MOR, β zeolite 250 460 7.10 mechanical mixtures Comp. Ex. 8 ZSM-5, β zeolite 240 460 5.40 mechanical mixtures

TABLE 13 Phase Composite molecular sieve Mechanical mixture contained Ethylene Propylene Diolefine Ethylene Propylene Diolefine therein yield yield yield yield yield yield Examples (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) Comp. Ex. 1 ZSM-5 35.02 12.53 47.55 30.2 12.0 42.2 Comp. Ex. 2 MOR 35.5 13.1 48.6 29.4 13.2 42.6 Comp. Ex. 3 Y zeolites 33.42 10.83 44.25 30.1 11.6 41.7 Comp. Ex. 4 β zeolites 32.72 10.87 43.59 27.7 12.6 40.3 Comp. Ex. 5 ZSM-5, MOR 31.4 12.6 44.0 29.8 11.6 41.4 mechanical mixtures Comp. Ex. 6 ZSM-5, Y 32.6 13.0 45.6 28.6 12.1 40.7 zeolite mechanical mixtures Comp. Ex. 7 MOR, β 31.3 14.2 45.5 30.2 10.1 40.3 zeolite mechanical mixtures Comp. Ex. 8 ZSM-5, β 33.5 12.6 46.1 30.3 11.2 41.5 zeolite mechanical mixtures Note: reviewing under the conditions of a reaction temperature of 650° C., a reaction pressure of 0.15 MPa, a water/feedstock mass ratio of 3:1 and a weight hourly space velocity of 1.0 h⁻¹. 

1. A catalyst for catalytic cracking fluidized-bed, comprising a support and a composition having the following chemical formula, which is on the basis of atom ratio: A_(a)B_(b)P_(c)O_(x), wherein A therein is at least one selected from the group consisting of rare earth elements; B is at least one element selected from the group consisting of VIII, IB, IIB, VIIB, VIB, IA and IIA; a ranges from 0.01-0.5; b ranges from 0.01-0.5; c ranges from 0.01-0.5; and X is the total number of oxygen atoms satisfying the requirements on the valence of each of the elements in the catalyst; wherein the support is composite molecular sieves or a mixture of composite molecular sieves and at least one selected from the group consisting of SiO₂ and Al₂O₃, and said composite molecular sieves are the composite co-grown by at least two molecular sieves selected from the group consisting of ZSM-5, Y zeolite, β zeolite, MCM-22, SAPO-34 and mordenitee, wherein the molecular sieves in the catalyst are in an amount of 0-60% by weight of the catalyst.
 2. The catalyst for catalytic cracking fluidized-bed according to claim 1, characterized in that a ranges from 0.01-0.3; b ranges from 0.01-0.3; and c ranges from 0.01-0.3.
 3. The catalyst for catalytic cracking fluidized-bed according to claim 1, characterized in that the rare earth element is at least one selected from the group consisting of La and Ce.
 4. The catalyst for catalytic cracking fluidized-bed according to claim 1, characterized in that the VIII group element is at least one selected from the group consisting of Fe, Co and Ni; the IB element is at least one selected from the group consisting of Cu and Ag; the IIB element is Zn; the VIIB element is Mn; the VIB element is at least one selected from the group consisting of Cr and Mo; the IA element is at least one selected from the group consisting of Li, Na and K; and the IIA element is at least one selected from the group consisting of Mg, Ca, Ba and Sr.
 5. The catalyst for catalytic cracking fluidized-bed according to claim 1, characterized in that the composite molecular sift is at least one selected from the group consisting of ZSM-5/mordenite, ZSM-5/Y zeolite and ZSM-5/β zeolite.
 6. The catalyst for catalytic cracking fluidized-bed according to claim 1, characterized in that the silica alumina molar ratio SiO₂/Al₂O₃ of the composite molecular sieves ranges from 10 to
 500. 7. The catalyst for catalytic cracking fluidized-bed according to claim 6, characterized in that the silica alumina molar ratio SiO₂/Al₂O₃ of the composite molecular sieves ranges from 20 to
 300. 8. The catalyst for catalytic cracking fluidized-bed according to claim 1, characterized in that the molecular sieves are in an amount of 10-60% by weight of the catalyst.
 9. The catalyst for catalytic cracking fluidized-bed according to claim 1, characterized in that the molecular sieves are in an amount of 20-50% by weight of the catalyst.
 10. A method of catalytically cracking heavy oil, light diesel oil, light gasoline, catalytically cracked gasoline, gas oil, condensate oil, C4 olefin or C5 olefin, comprising using the catalyst for catalytic cracking fluidized-bed according to claim
 1. 11. A method of catalytically cracking naphtha, comprising using the catalyst for catalytic cracking fluidized-bed according to claim 1, wherein the reaction is carried out at a temperature of 580-650° C., a catalyst loading of 0.5-2 g naphtha/g catalyst·h, a water/naphtha weight ratio of 0.5-3:1, and a reaction pressure of 0-0.2 MPa. 